Cam type limit switch



' y 4, 1942. w. c. FURNAS ET AL. 9,

CAM TYPE LIMIT SWITCH 2 sheets-sheet 1 Filed June 9, 1941 ygAzak /)\1VEN TOPS A TTORNE vs July14, 1942. F RN L 2,289,643

CAM TYPE LIMIT SWITCH Filed June 9, 1941 2 Sheets-Sheet 2 w: ,4: /a 2/22 7' II /a 7 v 73- Q E g 5 /5 I I 3 "I /2 49 Z 1" o j0@, 3 l r 3. a In2 I v ATTORNEYS Patented July 14, 1942 CAM TYPE LIMIT SWITCH William C.Furnas and Gilbert H. Hansen, Batavia, 11].; said Hansen assignor tosaid Furnas Application June 9, 1941, Serial No. 397,228

6 Claims.

Our invention relates primarily to improvements in electric switchassemblages, and relates more particularly to various improvements inthe construction and operation of limit switches of the type wherein theswitch contacts are actuated mechanically with the aid of cam mechanismor the like.

An object of the present invention is to provide a new and useful camtype limit switch which is simple and compact in construction, and.which is also highly effective in use and flexible in its adaptations.

Another more specific object of our present invention is to provide animproved "cam type switch assemblage of the general class wherein aroller carried by the switch operating lever is cngageable with a cam orthe like carried by a moving device such as an elevator, the movement ofwhich is being controlled by the switch, to either make or break theelectrical circuit.

A further specific object of the invention is to provide an improvedlimit switch unit, which is durable in construction, and which is alsopositive, dependable and rapid in action.

Still another specific object of our invention is to provide an improvedcompactswitch assembly which can be quickly and conveniently adjusted,to effectively meet various conditions of operation, by merely changingthe relative positions of simple parts, or by replacing one of the partsby a similarly simple element.

An additional specific object of this invention is to provide amechanically actuated limit switch wherein the contacts are actuated byimproved cam mechanism of simple construction, and are operable toproduce a variety of actions.

Another specific object of the present invention is to provide anextremely compact and sturdy limit switch unit, all parts of which maybe readily constructed and assembled at minimum cost, and which ishighly efficient in operation.

These and other objects and advantages of the invention will be apparentfrom the following detailed description.

A clear conception of one embodiment of the invention; and of the modeof constructing and of utilizing the improved cam type limit switch,

' may be had by referring to the drawings accom- Fig. 2 is a sectionthrough the switch unit of Fig. 1, taken along the line 2-2;

Fig. 3 is a transverse section through the cas-r ing of the switch,taken along the line 3--3 of Fig. 4, and showing the actuating leverremoved and the other mechanism in elevation;

Fig. 4 is a front elevation or plan view of the normally concealedswitch mechanism, the enclosing cover having been removed;

Fig. 5 is a section through the switch contact assemblage taken alongthe line 5-5 of Fig.2, and showing the contact actuating the cam in oneposition of adjustment;

Fig. 6 is a section similar to that of Fig. 5, but showing the contactactuating cam in another position of adjustment; and Fig. 7 is atransverse section through the switch actuating mechanism, taken alongthe line '|--'I of Fig. 3.

While the features of the present invention have been shown herein asbeing embodied in a cam type roller and lever actuated limit switch of aparticular design, it is not, our desire 'to thereby unnecessarily limitor restrict the scope and utility of the improvement.

Referring to. the drawings, the improved cam type limit switch showntherein, comprises in general a main outer cup-shaped casing 9 havingopenings [0 in the rear wall thereof for effecting attachment of theswitch unit to a support, and being provided with a detachable closureplate or cover II; a supporting plate l2 removably secured to the rearwall of the casing 9 by screws 13, and having a bracket l4 rigidlyattached thereto and provided with front flanges l5 to which the cover II is detachably attachable by other screws l3; a switch contact supportand housing l6 rigidly secured to the plate l2 above the bracket l4 andhaving a removable top plate H; a pair of laterally separated fixedcontacts l8 rigidly secured within the housing l6 and having terminalattaching screws l9; a pair of similarly spaced movable contacts 20flexibly suspended from a fiat guide bar 2| slidably penetrating thehousing l6, and coacting with a compression spring 22 which reactsagainst the plate I1; a fixed stub shaft 23 rigidly secured to thesupporting plate l2 beneath the bracket l4 and having a threaded socket24 at its outer end beyond the cover II; a hollow hexagonal shaft 25journalled for rotation on the fixed stub shaft 23 and having a cam 26firmly attached to its inner end in the plane of movement of the contactcarrier bar 2|, while its outer end is provided with screw threads 21; asleeve 28 embracing the medial hexagonal portion of the shaft 25 andcoacting at its inner end with the flat cam 26;

lever 29 and sleeve 28 in place; and torsion spring mechanism associatedwith the inner end of the stub shaft 23 and being cooperable with thecam 26 in various positions of adjustment to effect automatic actuationof the movable contacts 20.

The main casing 9, cover supporting plate |2, bracket l4, switchcontacts I8, 29, cam 26, and lever 29, may all be formed of sheet metalwith the aid of punches and dies, and are preferably coated to preventrusting. The contact supporting and protecting housing l6, top plate l1,and guide bar 2| are preferably formed of durable insulating material,and the movable contacts 29 may be flexibly suspended from the carrierbar 2| in order to insure proper engagement with the fixed contacts l8when the switch is closed as in Fig. 6. The upper end of the spring 22may be confined within a recess 36 in the top plate H as shown in Figs.5 and 6, in order to retain the spring in place, and the fiat bar 2|should be freely slidable in the housing 6 and is constantly urgedtoward the cam 26 by the spring 22. One side of the main casing 9 mayalso be provided with openings, not shown, for introducing theconducting wires into the switch enclosure so that they may be attachedto the terminal screws l9.

The fixed stub shaft 23 may be provided with an enlarged base portion 31as shown in Figs. 2 and 7, and the flat cam 26 is provided with ahexagonal central hole snugly engaging the outer hexagonal surface ofthe shaft 25 which is journalled on the outer smaller portion of theshaft 23. The end of the hollow shaft 25 adjacent to the enlargedportion 31 of the bearing shaft 23, is provided with a fixed plate 38forming a stop for the cam 26, and this cam may be removed endwise fromthe opposite end of the shaft 25 and applied thereto in differentangular positions with respect to the shaft axis. The cam 26 is ofapproximately heart shape as shown, and has a pointed lobe 39 and twoside lobes 40 separated by a depression 4|. Each of the side lobes 40 isseparated from the central lobe 39 by an abutment 42, and when the cam26 is applied to the shaft 25 as in Fig. 5, the movable contacts 20 willbe held in open position by the cam when the latter is centrallydisposed, and will be moved into closed position by the spring 22 whenthe cam is oscillated in either direction from central position. Whensuch oscillation occurs, the abutments 42 will function to stop or limitthe extent of swing of the cam 26, by engagement of the abutments withthe end of the bar 2| but these abutments 42 will not ordinarily g1,come effective and act merely as safety devices. When the cam 26 isreversely applied to the shaft 25 as shown in Fig. 6, the movablecontacts 20 will be held in closed position by the spring 22 when thecam is centrally located, and will be moved into open position by thecam lobes 49 when the cam 26 is oscillated in either direction fromcentral position. The improved cam 26 is also provided with an eccentricpin 43 projecting rearwardly therefrom, the function of which will belater explained.

The sleeve 28 which embraces the hexagonalportion of the shaft 25 servesprimarily to keep the cam 26 against the stop plate 38 and in properposition with respect to the bar 2|, and this sleeve 28 snugly engagesthe corners of the hexagonal shaft portion. The sleeve 28 however alsoserves as an abutment for properly positioning the lever 29 upon thehexagonal shaft 25, and the star opening 3|] is so formed that the lever29 may be applied to the shaft 25 in various positions of angularadjustment about the shaft axis. The actuating roller 32 and lever 29may thus be associated with the hexagonal shaft 25 in different angularpositions relative to the cam 26, and the cam may also be associatedwith this same shaft in various angular positions, thereby making theassemblage very flexible and adapted for operation under diverseconditions. As previously indicated, the screw 33 serves to retain thehollow shaft 25 upon the fixed bearing shaft 23; and the nut 34 and lockwasher 35 serve to retain the lever 29 attached to the shaft 25 and alsomaintain the sleeve 28 and cam 26 in place, and the position of thelever 29 may be varied without removing the cover The improved torsionspring mechanism for automatically returning the cam 26 and lever 29 topredetermined position, after oscillation of the lever 29 in eitherdirection has been efiected, is

best shown in Figs. 2, 3 and 7, and comprises a plate 44 rigidly securedto a spool or hub 45 journalled on the enlarged portion 37 of the fixedshaft 23, and having an integral laterally projecting lug 46 and twodiametrically opposite holes 41 interchangeably cooperable with the campin 93; a torsion spring 48 embracing the hub 45 and having oppositeoutwardly projecting ends 49, 59 disposed on opposite sides of the lug46; and a pin 5| rigidly secured to the supporting plate i2 and disposedbetween the torsion spring ends 49, 50. The plate 44 may be formed ofsheet metal, and is also provided with inclined peripheral projections52 adapted to limit the extent of oscillation thereof about the shaft23; and the lug 46 and pin 5| may be provided with notches for retainingthe spring ends 49, 59 in proper position. This torsion springassemblage is so constructed and arranged, that the cam projection 43may be caused to cooperate with either of the holes 41 in the disk orplate 44, and when the shaft 25 and cam 26 are subsequently oscillatedin either direction, either spring end 49, 56 will be moved away fromthe fixed pin 5| while the other spring end will be held againstmovement, thereby causing the spring 49 to be wound about its axis andplaced under higher tension. When the oscillating force is released, thespring 48 will act quickly to return both of its ends 49, 56 intoengagement with the pin 5|, and the cam 26, shaft 25, and lever 29 willthus be automatically returned to initial or predetermined inactiveposition.

During normal use of the improved cam type limit switch, it is firstnecessary to properly position the cam 26 with respect to its carryingshaft 25, and to likewise properly position the lever 29 with respect tothis shaft 25, so as to produce the desired operation of the switch atthe desired moment. If the cam 26 and lever 29 are secured to the shaft25 in the relative positions shown in Fig. 5, the movable contacts 20will normally be out of engagement with the fixed contacts I8. If theroller 32 and lever 29 are subsequently shifted to either ofthe'positions shown in dotthe movable contacts 20 will normally beclosed and in engagement with the fixed contacts 18;

' and movement of the lever 29 and roller 32 to either the dotted ordot-and-dash positions, will cause the lobes 40 of the cam 26 to engagethe actuating bar 2| and to thereby open the switch.

' Release of the actuating pressure on the roller 32,

will again cause the cam 26 to assume central position and will therebypermit the spring 36 to become effective to close the contacts. Thisoperation will again be automatically accomplished by the torsion spring48, in an obvious manner. It will be understood that the position of theactuating lever 29 with respect to the shaft 25 may be readily varied tosuit different conditions of operation, by merely releasing the nut 34and adjusting the lever 29 upon the shaft 25.

From the foregoing detailed description of the construction andoperation of the -improved switch, it will be apparent that the presentinvention provides an improved cam type limit switch which besides beingsimple and durable in construction, is extremely flexible in itsadaptations and efficient in operation. The various adjustments can bequickly and readily accomplished without the use of special tools, andthe improved cam 26 makes .it possible to have the switch either open orclosed when the mechanism is in central or neutral position.

All of the elements of .the assemblage are readily accessible forinspection and adjustment, and all parts may be readily constructed andassembled. The casing 9 and cover H provide an effective housing for theworking parts, while permitting adjustment of the lever 29 withoutremoving the cover. The contact support I6 operates with the top plateI! to effectively house and protect the contacts, and the bracket I4 isso constructed that the conductor wires may be readily applied to theterminals I9 without danger of having the wires interfere with thenormal operation of the cam mechanism. The improved switch assemblagehas proven highly satisfactory in actual use, and maybe manufactured andsold at moderate cost since most of the elements are adapted to beformed of sheet metal with the aid of punches and dies.

While the invention has been shown and de scribed herein as beingembodied in a cam type limit switch having a single cam 26 of definiteshape, and wherein the contacts are either closed or open when the 'camis in central or mid-position, it should be clearly apparent that morethan one-cam may be mounted on the same to limit this invention to theexact details of construction or to the precise mode of use, herein sonsskilled in the art.

We claim:

1. In combination, a casing, a stub shaft having one end fixedly mountedwithin said casing, a motion transmitting element slidably confinedwithin said casing and being movable toward and away from the axis ofsaid shaft, means for constantly urging said element toward said shaft,a hollow externally polygonal shaft journalled for oscillation upon saidfixed shaft and having one end disposed within said casing in the pathof movement f said element,-a cam mounted upon said hollow shaft andcoacting with said element to move the latter away from said axis, meanscarried by said stub shaft and coacting with said cam to constantly urgesaid hollow shaft into .a predetermined position relative to said axis,and a lever mounted upon said hollow shaft remote from said cam, saidlever and said cam each having a polygonal opening snugly engageablewith the polygonal exterior of said hollow shaft in different angularpositions relative to said axis so as to permit independent adjustmentof said cam and lever about said axis. I

2. Mechanism as per claim 1, characterized thereby, that a sleeve snuglyembraces the poshaft 25 and caused to operate more than one lygonalouter portion of said hollow shaft and coacts with said cam and lever todefinitely space said elements apart. I

3. Mechanism as per claim 1, characterized thereby, that said casing isprovided with an enclosing cover which is pierced by the outer ends ofsaid stub and hollow shafts, and that said lever is detachably securedto said hollow shaft outside of said casing and cover,

4. Mechanism as per claim 1, characterized thereby, that the means forconstantly urging the motion transmitting element toward the stub shaftis a spring, and that the means coacting with the cam for constantlyurging the hollow shaft into a predetermined position is a torsionspring carried by a hub snugly embracing the fixed end of said stubshaft.

5. Mechanism as per claim 1, characterized thereby, that said hollowshaft is retained endwise upon said stub shaft by a set screw coactingwith the adjacent outer ends of these shafts, and that said lever isheld in place upon said hollow shaft by a nut which is removable withoutremoving said set screw.

6. Mechanism as per claim 1, characterized thereby, that said hollowshaft is retained endwise upon said stub shaft by a set screw coactingwith the adjacent outer ends of these shafts, and that said lever isheld in place upon said hollow shaft by anut which is removable withoutremoving said'set screw, and characterized thereby, that both said leverand said spacing sleeve are held in place upon said hollow shaft by thenut which is removable without removing said set screw, and that saidlever. and sleeve are also thus removable from the hollow shaft.

WILLIAM c. roams GILBERT H. naigsai

